United States country profile
The USA is the world's foremost economic and military power, with global interests and an unmatched global reach.
America's gross domestic product accounts for close to a quarter of the world total, and its military budget is reckoned to be almost as much as the rest of the world's defence spending put together.
The country is also a major source of entertainment: American TV, Hollywood films, jazz, blues, rock and rap music are primary ingredients in global popular culture.
The United States originated in a revolution which separated it from the British Crown. The constitution, drafted in 1787, established a federal system with a division of powers which has remained unchanged in form since its inception.
President: Donald Trump
Republican candidate Donald Trump defeated Democratic candidate Hillary Clinton to win the presidency in the 2016 election. Mr Trump's victory was one of the biggest upsets in US political history, confounding the opinion polls and putting an end to eight years of Democratic control of the White House.
A billionaire businessman, reality TV star and political outsider, Mr Trump campaigned on a vow to "make America great again". He presented himself as an agent of change who would bring manufacturing jobs back to the US, tear up unfavourable trade deals, and curb illegal immigration.
During an election campaign generally regarded as the most acrimonious in living memory, Mr Trump drew accusations of racism and misogyny, and managed even to alienate many senior members of his own party. In office, his rhetoric has continued to divide Americans,
President Trump has renegotiated the North America Free Trade Agreement with Canada and Mexico, held talks with the North Korean leader Kim Jong-un, and imposed tariffs on Chinese imports.
He has less success in pushing through his domestic agenda on cutting migration and replacing the Democrats' public healthcare programme, but has managed to enact major tax cuts.
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The US has the most highly-developed mass media in the world. Its dramas, comedies, soaps, animations, music videos and films have a global audience and are staple fare for broadcasters worldwide.
It is the home of the internet; more than 88% of Americans are online and 79% of adults use Facebook.
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1565 - First permanent European settlement in North America.
17th-18th centuries - Hundreds of thousands of Africans brought over and sold into slavery to work on cotton and tobacco plantations.
1775 - American Revolution: George Washington leads colonist Continental Army to fight against British rule.
1787 - Founding Fathers draw up new constitution for United States of America. Constitution comes into effect in 1788.
19th century - Residual resistance by indigenous people crushed as immigration from Europe assumes mass proportions, with settlers moving westwards.
1861-1865 - US Civil War: Federalist forces defeat the Confederate pro-slavery states in the South. Slavery is abolished under the Thirteenth Amendment.
1929-33 - 13 million people become unemployed after the Wall Street stock market crash of 1929 triggers what becomes known as the Great Depression.
1941 - Japan attacks the US fleet at Pearl Harbour in Hawaii, precipitating the United States' entry into World War Two.
1954 - Racial segregation in schools becomes unconstitutional; start of campaign of civil disobedience to secure civil rights for Americans of African descent.
2001 11 September - Co-ordinated suicide attacks on various high-profile targets by the al-Qaeda jihadist group, prompting the US to embark on a ''war on terror'' which includes the invasion of Afghanistan and Iraq.
2008 - Barack Obama is elected the first black president of the United States.
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